1. FIELD OF THE INVENTION
The field of the present invention is wheel suspension systems for automobiles and particularly, is improvements of wheel suspension systems comprising a pair of upper and lower control arms linked at their leading ends to a knuckle for carrying a wheel, the upper and lower control arms being pivotally connected at one side of their base ends to a vehicle body for vertical swinging movement and being connected at the other side of their base ends to a pair of upper and lower support arms projectingly provided on a support shaft which is supported on the vehicle body through elastic members to extend longitudinally thereof.
2. Description of the Prior Art
A wheel suspension system similar to the above has already been proposed by the present applicant, as shown in Japanese Patent Application Laid-open No. 106119/88.
In such wheel suspension system, the support shaft is required to have a higher torsional rigidity, because it receives a large torsional load from the upper and lower support arms, particularly during braking. Thereupon, it is thought that the support shaft needs to be formed with a larger diameter to enhance its torsional rigidity. However, the entire support shaft having a larger diameter is not preferred, because it causes an increase in weight.